It is known that the metallic halides, in particular the halides of alkali metals or alkaline-earth metals, can be reduced with calcium carbide, thereby freeing the metal and carbon, according to the reaction: EQU aMX.sub.n + bCaC.sub.2 .fwdarw. aM + 2bC + bCaX.sub.2,
wherein M is a metal with a valence of n, X is a halogen atom, and the stoichiometric proportions are such that b/a = n/2.
In the known processes this reduction is carried out in a heterogeneous -- solid-solid, solid-liquid, or solid-gas -- medium. Such a process is difficult to perform continuously, which is necessary if one hopes to sell the product at a competitive price. That is probably the reason why up to the present, as far as we are aware, there has been no industrial application of this reaction.
U.S. Pat. No. 3,031,413, to Barber et al., teaches the reduction of a metal halide such as lead chloride by reacting it with a solution of calcium carbide in one or more substantially anhydrous, molten halides, specifically the halides of lithium, calcium, strontium and/or barium.